From the archives: 6-21-23




Touch DNA refers to the trace amounts of DNA that can be transferred through direct contact between an individual's skin cells and an object or surface. It is a valuable forensic tool used in crime scene investigations to help identify potential suspects or link individuals to a particular location.

When individuals touch an object or surface, they leave behind skin cells containing their DNA. Touch DNA analysis involves collecting and analyzing these minute samples to extract the DNA and generate a DNA profile. The DNA profile contains unique genetic markers that can be compared to known DNA samples, such as those from a suspect or a DNA database, to determine a potential match or identify an unknown individual.The process of touch DNA analysis typically involves the following steps:

1. Sample collection: Forensic investigators collect potential touch DNA samples from objects or surfaces at a crime scene using various techniques. This may involve swabbing the surface with a sterile cotton swab or using adhesive tape to lift any visible or invisible biological material.
2. DNA extraction: The collected samples undergo a DNA extraction process to isolate the DNA from other substances present on the surface. This step aims to purify the DNA and remove any potential inhibitors that might interfere with subsequent analysis.
3. DNA amplification: The extracted DNA is subjected to a process called polymerase chain reaction (PCR), which amplifies specific regions of the DNA. PCR allows for the generation of sufficient DNA material for further analysis, even if only a minimal amount of touch DNA was initially present.
4. DNA profiling: The amplified DNA is analyzed using techniques such as short tandem repeat (STR) analysis. STR markers are specific regions within the DNA that exhibit variations in the number of repeated DNA sequences. By comparing the lengths of these STR markers between the crime scene sample and a reference sample, a DNA profile is generated.
5. Database search and interpretation: The DNA profile obtained from the touch DNA sample can be compared to known reference samples from suspects or individuals in a DNA database. If a match is found, it can provide investigative leads or potentially establish a link between the individual and the crime scene.

It's important to note that touch DNA analysis has certain limitations. The amount of DNA left behind through touch is often very small, making it susceptible to contamination and degradation. Factors such as the environmental conditions and the time elapsed since the DNA was deposited can affect the quality and quantity of the touch DNA sample. Additionally, the presence of multiple individuals' DNA on an object or surface can complicate the analysis.

Nevertheless, touch DNA analysis has proven valuable in numerous criminal investigations, aiding in the identification of suspects, establishing links between individuals and crime scenes, and exonerating innocent individuals. It is a powerful tool in forensic science that complements other methods of DNA analysis, such as blood or saliva DNA samples.

"The comparison showed a statistical match—specifically, the STR profile is at least 5.37 octillion times more likely to be seen if Defendant is the source than if an unrelated individual randomly selected from the population is the source," the filing says according to the article.

In this episode we take a look at how strong that evidence is and how Kohberger's team might attempt to challenge it.

(commercial at 7:40)

to contact me:

bobbycapucci@protonmail.com



source:

Bryan Kohberger DNA Revelation Made in New Court Documents (newsweek.com)